The present invention relates to lock spindle blind fasteners and more particularly to lock spindle blind fasteners adapted to be set by a single action tool. Lock spindle blind fasteners, of the pull-type, are generally of two types; one in which the fastener is constructed to be set by a double-action tool and the other constructed to be set by a single action tool. The fastener of this invention is of this latter type. Both type of tools are generally well known in the fastener art.
Fasteners constructed to be set by a single action tool have had problems of load balance during different stages of setting the fastener including among other problems the supporting of the locking collar during the setting of the fastener which if not properly provided for can result in a malfunction in the final setting of the fastener. As a general rule these problems can be minimized if a fastener construction is utilized which requires low setting levels, i.e. relative force between pin and sleeve via the locking collar. As a result such fasteners have employed designs utilizing constructions requiring low setting loads. This has been accomplished in the past using constructions in which the mandrel and sleeve cooperate to provide tulip type head such as that shown in U.S. Pat. No. 3,915,055 issued Oct. 28, 1975 to L. S. Binns. A blind fastener having superior characteristics can be obtained where a mandrel and sleeve are used which cooperate to provide a bulbed head such as that shown in U.S. Pat. No. 2,061,628 issued Nov. 24, 1936 to L. C. Huck. One difficulty with bulbed head blind fasteners, however, is that the setting loads are considerably higher than those for a tulip type head.
In the present invention a fastener construction is provided in which a lock spindle blind fastener having a mandrel and sleeve constructed to cooperate to provide a bulbed head that can be set using a single action tool.
One form of a lock spindle blind fastener is shown and described in the parent case, Ser. No. 835,363 which case has claims directed to the solution of a problem with flush head fasteners; in that case the sleeve has a countersunk (flush) head configuration and a longitudinal, central tubular opening therethrough for the reception of the spindle or mandrel. The underside of the sleeve head is formed with an included angle of 106 degrees, plus or minus 2 degrees and is received within a countersunk hole of the workpiece in which the countersunk hole portion is conventionally 100 degrees, plus or minus 1 degree. There is thus an angular relationship between these facing surfaces of approximately 6 degrees from the outside in, before the fastener is set.
The longitudinal bore of the sleeve head has a straight-wall counterbore of approximately 0.015" and a communicating lock collar entry resistance angle of approximately 80 degrees.
The mandrel is received within the bore of the sleeve and has a head on its blind end adapted to engage the inner or blind end of the sleeve and form the blind head when the rivet is set, as in the prior art.
The mandrel is formed with a concealed break notch and a lock pocket, both known in the prior art.
A ring shaped lock collar embraces the projecting end of the mandrel and initially seats within the straight counterbore in the head of the sleeve. The projecting end of the lock collar is engaged by the nose of the setting tool and as the mandrel is pulled the reaction force of the nose presses the lock collar inwardly of the sleeve. The collar abuts against the entry resistance angle of the sleeve and movement into the lock pocket is restrained until the mandrel reaches the end of its pull stroke when the collar is forced into the lock pocket of the mandrel.
As will be seen the features of the present invention can be applied to fasteners having sleeves with flush or protruding head constructions; these features, many of which are disclosed in the noted parent case, are directed more to overall balancing of loads whereby an effective fastener design can be realized having high strength characteristics.